1. Field of the Invention
The present invention relates to a capacitor electrode, a method for manufacturing the capacitor electrode, and a semiconductor device comprising a capacitor.
2. Description of the Related Art
Along with the recent progress in the miniaturization of semiconductor devices, a high-dielectric constant film has become necessary as a dielectric film for capacitors used in, for example, DRAMs of a generation in which the F value is 40 nm (40 nm-design rule generation and beyond). Hence, SrTiO3 and the like have now been proposed as major candidates for that film.
A TiN/Ti electrode has been used conventionally as a capacitor electrode. Furthermore, there has been a need for an electrode having a high work function as a capacitor electrode including a high-dielectric constant film. Thus, a study has been made in recent years of electrode materials. For example, Pt can be mentioned as a material having the highest work function.
C. M. Chu, et al., Symp. On. VLSI Tech, Dig., 2001, T4B-3 discloses a capacitor comprising an Ru/SrTiO3/Ru MIM structure (Metal-Insulator-Metal structure, i.e., a capacitor structure in which upper and lower electrodes are formed of metal films) in which Ru (ruthenium) is used as an electrode material. In the capacitor described in C. M. Chu, et al., Symp. On. VLSI Tech, Dig., 2001, T4B-3, the crystal quality of a dielectric film (SrTiO3) is improved by performing a heat treatment after fabricating the Ru/SrTiO3/Ru MIM structure, thereby reducing the leakage current value of the capacitor.
Joon Seop Sim et al., J. Electrochem. Soci., 153 (11) C777-C789 (2006) discloses an example in which an electrode made of an SrRuO3 film containing Sr (strontium) and Ru is used as another electrode material. The crystal structure of this SrRuO3 film is a perovskite structure identical to that of high-dielectric SrTiO3 and the like. Use of this SrRuO3 film has the advantage of being able to epitaxially grow a high-dielectric film and improve the crystal quality. Accordingly, it is possible to obtain a higher-quality film having a larger dielectric constant, compared with other electrode materials using SrRuO3. In addition, since this SrRuO3 has a high work function, it is a focus of attention as a promising material also for the reduction of a leakage current value.
I have now discovered that a capacitor electrode having a specific composition has a small electrical resistance value and is capable of suppressing an increase in the leakage current value in a capacitor including the capacitor electrode and a high-dielectric constant film as an insulator.